As per Moore's law, advances in integrated circuit (IC) technologies have resulted in decreasing the size and operating voltages of devices used to fabricate circuitry. As process geometries are shrinking, the voltages required for support are also decreasing. For example, in CMOS 28 nm process, standard voltage core devices support 0.9V input supply voltage while preferred thick oxide devices in this process support 1.8V input supply. There is a trend of lower supply voltages for core and IO (thick oxide) devices.
In battery operated devices, such as cellular phones, smartphones, tablets, and laptop computers, low-voltage integrated circuits allow the devices to operate proportionally longer than devices requiring higher voltage for operation. The lower supply voltages of the latest standards (e.g. USB3.0, SATA3.0, PCIe3 etc.) may not always be compatible with legacy host device interfaces but new interfaces are typically backwards compatible. For example, old standard hosts provide higher supply voltage than new standards. Many interface standards are still supporting higher voltages, including 5V, 3.3V or 2.5V along with lower voltages (from host devices) for analog design or for maintaining compatibility with older interface standards. Accordingly, regulators need to translate 3.3V to 1.8V or 3.3V to 0.9V or lower with devices whose typical operational voltage is 1.8V or lower. Maximum possible support for these 1.8V devices can be up to 2V but not necessarily up to 3.7V or so.
The latest computer peripheral devices may therefore be designed to accommodate connections from newer, lower voltage host supplies as well as older, higher voltage supplies. Devices constructed with newer technologies therefore must allow for the possibility that the host device in which they are used may supply a higher voltage with legacy products. In order to couple systems manufactured with newer interface standard technologies to legacy interface standard hosts that provide higher-supply voltages, voltage regulation from higher voltage to lower voltage with devices whose operating voltage is lower than the input supply voltage may be used to provide the correct voltage in steady state. However, the voltage regulation may not adequately handle this higher than operational voltage at start-up.